Groove Spacing Research Articles

Mechanism of methane adsorption on groove space in organic matter surface

ABSTRACTOrganic matter plays an important role in methane adsorption in shale. Pore surface of organic matter is usually rough and uneven, which results in a large amount of groove space on the pore surface. Thus, the influence of groove space on the adsorption capacity of methane in shale cannot be neglected. Nanoscale pore structures of the organic-rich shale in the Longmaxi Formation were investigated by low-pressure nitrogen gas adsorption as a basis for constructing models. We simplified the internal groove space into triangular prisms with different angles. The grand canonical Monte Carlo simulation and molecular dynamics simulation were used to analyse the methane molecule adsorption behaviour in pores. The results showed that the pore morphology of organic-rich shale in the Longmaxi Formation was mainly slit-shaped pores. The excess adsorption isotherms showed good agreement between experiment and simulation, indicating that the model is suitable and reliable. Methane molecules can enter into the groove space with an opening size of 0.738 nm, while they fail to enter into groove spaces with an opening size less than 0.492 nm. This understanding has important significance for the study of the adsorption characteristics of organic pores which have undergone multiple evolutions in geological history.

Ultrasensitive Wearable Pressure Sensors Assembled by Surface-Patterned Polyolefin Elastomer Nanofiber Membrane Interpenetrated with Silver Nanowires.

Wearable pressure sensors with ultrahigh sensitivity and flexibility have garnered tremendous attention because of their abilities to mimic the human somatosensory system and perceive surrounding pressure distribution. Herein, an ultrasensitive pressure sensor was fabricated with surface-patterned nanofibrous membranes (SPNMs) via a facile replica method from available plain-weaved nylon textiles. The SPNMs were composed of internal three-dimensional interpenetrating polyolefin elastomer nanofibers and silver nanowires (Ag NWs). The effects of the geometry of surface patterns and the density of the Ag NW network on the sensing performance of the assembled pressure sensor were systematically investigated. The results indicated that clavate groove-shaped surface patterns improved the sensitivity and a larger groove spacing contributed to higher sensitivities, whereas denser Ag NWs would reduce the sensing performance. The optimal pressure sensor assembled with SPNMs-45 and a Ag NW fraction of 3.8% showed high sensitivity (19.4 kPa-1) below the pressure of 2.76 kPa, a low detection limit (<1.6 Pa), fast response (30 and 42 ms), as well as excellent durability. These outstanding performances demonstrated its promising potential for wearable electronic applications, like detecting the spatial pressure distribution and monitoring human muscle motions.

Epoxy interlocking: A novel approach to enhance FRP-to-concrete bond behavior

This paper presents a novel approach which can enhance the interfacial bond behavior between fiber reinforced polymer (FRP) composite material and concrete. Epoxy ribs are formed by grooving on the concrete surface before epoxy is applied. The dowel action from the epoxy ribs leads to an “epoxy interlocking” effect. The mechanism of the proposed epoxy interlocking approach was analyzed in this paper from both adhesion and interlocking aspects. Furthermore, the partial interaction of the epoxy interlocking was quantified and calibrated by experimental results. The epoxy interlocking in the tested specimens led to an 88.8% increase in bond strength on average. An analytical approach was proposed to quantify the average partial interaction for the individual epoxy ribs. The load-slip relationship for individual epoxy ribs was found to be related to concrete compression behavior. A parametric study was conducted analytically on the effects of groove depth and spacing, concrete strength and epoxy rib location. The reasonable results in the parametric study further verify the efficiency of the epoxy interlocking to enhance the bond performance between FRP and concrete.

Lateral retinacular release via a prolonged incision versus arthroscopic lateral retinacular release in osteofascial medial patellofemoral ligament reconstruction for recurrent patellofemoral dislocation

Objective To compare the short-term outcomes between lateral retinacular release (LRR) via a prolonged incision versus arthroscopic LRR in osteofascial medial patellofemoral ligament reconstruction (MPFL-R) for recurrent patellofemoral dislocation. Methods From May 2012 to March 2015, 51 patients with recurrent patellofemoral dislocation were treated at the Department of Joint Surgery, The Third Affiliated Hospital to Hebei Medical University. They were 16 males and 35 females, aged from 20 to 36 years (mean 27.2 years). Of them, 28 underwent LRR via a prolonged incision in MPFL-R (incision group) and 23 did arthroscopic LRR in MPFL-R (microscopic group). Imaging changes were assessed by comparing preoperative and postoperative values of patella extensibility, patellar tilt angle, trochlear groove angle and tibial tuberosity-trochlear groove spacing (TT-TG); the knee joints were scored with Kujala and Lysholm functional rating systems at the last follow-ups. Results The 2 groups were compatible due to insignificant differences in the general data between them preoperatively (P>0.05). The 51 patients were followed up for 10 to 32 months (average, 20 months). The rate of dislocation in the incision and microscopic groups were 0 and 8.7% (2/23), respectively. There were no such complications in either group as patellar fracture, deep venous thrombosis of the lower extremity or limited joint extension or flexion. The last follow-ups revealed that no patients in either group were inflicted with patellofemoral re-dislocation. In the incision group, the patella extensibility, patellar tilt angle, Kujala score and Lysholm score were, respectively, 19.65%±0.75%, 12.39°±0.76°, 56.37±2.94 points and 51.64±6.22 points preoperatively, and 10.34%±0.60%, 8.83°±0.89°, 92.68±2.75, and 90.71±1.91 points postoperatively; in the microscopic group, the patella extensibility, patellar tilt angle, Kujala score and Lysholm score were, respectively, 19.56%±0.62%, 12.35°±0.66°, 57.46±3.08 points and 52.20±6.94 points preoperatively, and 10.24%±0.66%, 8.78°±0.92°, 92.53±3.32 points and 90.41±2.90 points postoperatively. There were significant differences between the preoperative and postoperative values in both 2 groups (P 0.05). There were no significant differences between the 2 groups in all the above preoperative and postoperative values (P>0.05). Conclusion In MPFL-R for recurrent patellofemoral dislocation, both LRR via a prolonged incision and arthroscopic LRR can improve the patellofemoral joint alignment and stability of the tibia, leading to good short-term outcomes. Key words: Arthroscopy; Patellar ligament; Patellar dislocation; Lysis

Mode coupling interaction for transverse electric (TE) fields in a groove doublet configuration

Based on the waveguide mode (WGM) method, the formulation of total scattered field including coupling interaction has been extended from the TM field to TE field. The calculated results show that there exists a damped oscillation with increasing groove spacing. For the case of two subwavelength grooves, the coupling interaction for the TE case is not sensitive to the incident angle and scattering angle and weaker than that for the TM case. The angle dependence for the TE field for two subwavelength is asymmetric while that for the TM field is symmetric. We offer a road to study and design metallic gratings in Terahertz and microwave region.

The effect of gravitational settling on concentration profiles and dispersion within and above fractured media

The transport of heavy particles in a medium that consists of fluid and solid phases such as stream gravel beds, cracked soils and wetlands is affected by processes such as attachment-detachment, gravity and drag, and by mixing processes that are induced by Taylor dispersion and mechanical dispersion. This paper addresses an additional dispersion mechanism which is induced by gravitational settling and is a result of the coupling between the particle concentration and the fluid velocity profiles at the sub-scale. Heavy particles that move in areas of low horizontal velocity (e.g., near solid surfaces and wake regions) settle closer to the release source as compared to particles in high velocity regions. The macroscopic concentration field of such suspensions is influenced by the ratio between the settling velocity and the sub-scale distribution of the horizontal velocities. The objective of the study is to isolate and quantify this type of dispersion using controlled flow scenarios. We used a Taylor brush geometry (an array of vertical grooves) to numerically solve the flow. Particles were released from a vertical plane, generating a constant flux. The sub-scale Eulerian concentration was compiled from simulated trajectories and then spatially averaged to generate macroscopic concentration fields. The results show that this settling-induced dispersion is significant in regions near the source and that it cannot be modeled using Fick's law type of formulations. A parametric investigation shows that the location of the highest dispersion flux is linearly proportional to both the groove spacing and depth. A proposed model that estimates this location is used to evaluate where settling-induced dispersion should not be ignored.

Storm-wave development of shore-normal grooves (gutters) on a steep sandstone beach face

Shore-normal grooves (gutters) cut into the seabed have been reported widely from the marine geological record. Grooves commonly are spaced regularly across plane, consolidated surfaces in the littoral and sub-littoral zones and may be deeply incised. Despite their common occurrence in the rock record, there are few detailed descriptions of examples from modern environments. Previously reported examples have been ascribed to erosion by wave-induced currents, especially storm-driven near-shore flows. In particular, examples from beach faces have been related to either wave swash or backwash. However, no conceptual model exists to explain the presence of grooves, their morphology or their spacing alongshore.Herein, quasi-regularly spaced grooves on a soft sandstone beach face are described and interpreted to have formed due to wave breaking and swash zone processes consequent upon exceptional storms at sea. The groove morphologies are quantified using terrestrial laser scanning. Numerical modelling of the translation from offshore waves to nearshore breaking waves provides estimates of the swash zone parameters. A consideration of swash zone processes provides an explanation for formation of the grooves. In particular, the swash zone shear stress distribution and consequent bed erosion is a dome-shaped function of distance across the beach face, and this controls the cross-shore variability in groove depths. High-speed sheet flows, such as swash and backwash, develop periodic, shore normal, high and low speed streaks alongshore. Consequent streaky erosion produces the quasi-regular alongshore groove spacings. However, on any given beach face the specific spacing of grooves is likely a property, not only of the local sheet flow attributes, but also of larger-scale morphological forcing. This outcome suggests that spacing is an emergent property of the coupled sheet flow and larger-scale forcing, and thus specific spacings on any beach face remain unpredictable.

A Cross-Sectional Study Into the Prevalence of Dairy Cattle Lameness and Associated Herd-Level Risk Factors in England and Wales

Lameness is one of the most pressing issues within the dairy industry; it has severe economic implications while causing a serious impact on animal welfare. A study conducted approximately 10 years ago found the within farm lameness prevalence in the UK to be 36.8%. Our objective here is to provide an update on within farm lameness prevalence in the UK, and to provide further evidence on farm level risk factors. A convenience sample of 61 dairy farms were recruited across England and Wales from September 2015 to December 2016. A single farm visit was made and the milking herd was mobility scored, as the cows exited the milking parlor after morning, afternoon, or evening milking. Information regarding the farm and management system was then collected using a short interview with the farmer followed by collection of various subjective and objective measurements of the environment. The same, trained researcher performed all animal and facility-based measures on all visits. A series of univariable analyses were conducted to evaluate the association between various risk factors and herd lameness prevalence (logit transformed). A multivariable linear regression model was then fitted. The median number of milking cows per herd was 193, ranging from 74 to 1,519 cows. The mean within farm lameness prevalence was 31.6%, ranging from 5.8 to 65.4%. In total, 14,700 cows were mobility scored with 4,145 cows found to be lame (28.2%). A number of risk factors were associated with lameness at the univariable analysis level. Categorical risk factors retained in the final model were: resting area type, collecting yard groove spacing width, whether farms were undertaking the 60- to 100-day post calving claw trimming and the frequency of footbathing in the winter. The amount of concentrates fed in the milking parlors or out of parlor feeders was also associated with lameness prevalence. The results of this study have provided an update on the UK herd lameness prevalence and have confirmed the importance of cow comfort and footbathing frequency. The association between early lactation claw trimming and reduced lameness prevalence is, to the best of our knowledge, reported for the first time.

Stability of the Poiseuille Flow in a Channel with Comb Grooves

The stability of the Poiseuille flow in a channel with longitudinal comb grooves on the lower wall is studied numerically. Dependences of the linear and energy critical Reynolds numbers on the groove spacing and height are obtained and analyzed. The results are compared with data available for wavy grooves, which tend to comb grooves as one of the groove parameters approaches infinity.

Hydrodynamic Lubrication of Micro-Grooved Gas Parallel Slider Bearings with Parabolic Grooves

The hydrodynamic lubrication performance of micro-grooved gas parallel slider bearings with parabolic grooves is investigated in this paper. By using the multi-grid finite element method, the pressure distribution between a micro-grooved slider and a smooth slider is obtained. The geometric parameters of the parabolic grooves are optimized to maximize the average pressure under a given sliding speed. The numerical results show that geometric parameters such as groove depth, width, spacing, and orientation angle have an important influence on hydrodynamic pressure. Furthermore, the effect of sliding speed on hydrodynamic pressure is investigated under a given set of groove depths. It is observed that there is an optimum value of sliding speed to maximize the average pressure for any given groove depth and that the optimum value is dependent of the groove depth. The results of this study indicate that the average pressure could be improved by employing the optimized groove depth according to the practical sliding speed. DOI: http://dx.doi.org/10.5755/j01.mech.23.6.19850

Experimental Studies on Grooved Double Pipe Heat Exchanger with Different Groove Space

Experimental studies were performed on grooved double pipe heat exchanger (DPHE) with different groove space. The objective of this work is to determine optimal heat transfer parameter especially logarithmic mean temperature difference (LMTD). The document in this paper also provides the total heat observed by the cold fluid. The rectangular grooves were incised on outer surface of tube side with circumferential pattern and two different grooves space, namely 1 mm and 2 mm. The distance between grooves and the grooves high were kept constant, 8 mm and 0.3 mm respectively. The tube diameter is 20 mm and its made of aluminium. The shell is made of acrylic which has 28 mm in diameter. Water is used as the working fluid. Using counter flow scheme, the cold fluid flows in the annulus room of DPHE. The volume flowrate of hot fluid remains constant at 15 lpm. The volume flowrate of cold fluid were varied from 11 lpm to 15 lpm. Based on logarithmic mean temperature difference analysis, the LMTD of 1 mm grooves space was higher compared to that of 2 mm grooves space. The smaller grooves space has more advantage since the recirculating region are increased which essentially cause larger heat transfer enhancement.

Nanosecond laser ablated copper superhydrophobic surface with tunable ultrahigh adhesion and its renewability with low temperature annealing

Recently, metallic superhydrophobic surfaces with ultrahigh adhesion have got plentiful attention on account of their significance in scientific researches and industrial applications like droplet transport, drug delivery and novel microfluidic devices. However, the long lead time and transience hindered its in-depth development and industrial application. In this work, nanosecond laser ablation was carried out to construct grid of micro-grooves on copper surface, whereafter, by applying fast ethanol assisted low-temperature annealing, we obtained surface with superhydrophobicity and ultrahigh adhesion within hours. And the ultrahigh adhesion force was found tunable by varying the groove spacing. Using ultrasonic cleaning as the simulation of natural wear and tear in service, the renewability of superhydrophobicity was also investigated, and the result shows that the contact angle can rehabilitate promptly by the processing of ethanol assisted low-temperature annealing, which gives a promising fast and cheap circuitous strategy to realize the long wish durable metallic superhydrophobic surfaces in practical applications.

Aperiodic nature of nanograting inscribed by femtosecond pulses

A systematic study was performed, both experimentally and theoretically, to investigate the structural periodicity of nanogratings inscribed by focused femtosecond pulses on the surface of dielectrics. The results surprisingly show that although nanogratings generally appear periodic they are in fact intrinsically aperiodic. In the perpendicular writing scheme, the groove spacing gradually decreases from the middle part towards both sides. In the parallel writing scheme, the groove spacing varies quasiperiodically and the variation differs with respect to pulse-to-pulse spacing. Constant groove spacing was obtained only for a particular pulse-to-pulse spacing. These Gaussian-apodized and quasiperiodic variations are found to be intrinsic. They arise from the fact that the grooves are created, depending on the writing scheme, either by a series of local-lobes with different amplitudes and material feedbacks or by a repeated generated leading side-lobe with similar but not identical amplitudes and material feedbacks. The production of each single grooves result from a nonlinear and localized process from which arises its aperiodic nature. All these intrinsically Gaussian-apodized and quasiperiodic variations can be well interpreted based on the incubation-based nanoplasmonic model.

Effect of groove spacing on bond strength of near-surface mounted (NSM) bonded joints with multiple FRP strips

In the strengthening of existing deficient structures using the near-surface mounted (NSM) FRP method, a group of parallel NSM FRP strips are usually needed to meet the capacity enhancement requirement. When the groove spacing (i.e., the net distance between grooves) is relatively small, the bond behaviour of each NSM FRP strip is detrimentally influenced by the adjacent grooves/FRP strips, and such detrimental effect should be taken into account for a safe design of the NSM FRP strengthening system. All the existing models, however, have been proposed for NSM bonded joints with a single FRP strip and thus cannot consider the effect of groove spacing on the bond behaviour, due to the insufficiency of data from tests or numerical simulations. Against this background, a numerical parametric study, was conducted to clarify the effect of groove spacing on the bond strength of such bonded joints; the numerical parametric study involved the use of a three-dimensional meso-scale finite element model developed in the present study for NSM bonded joints with two FPP strips separately embedded in two parallel grooves. Based on the results from the parametric study, a reduction factor to account for the detrimental effect of insufficient groove spacing on the bond strength is proposed and extended to NSM bonded joints with three or more evenly-spaced FRP strips. By combining the proposed reduction factor and the bond strength model previously developed by the authors for NSM bonded joints with a single FRP strip, a bond strength model for NSM bonded joints with multiple FRP strips is proposed and the accuracy of the proposed model is verified with test results.

Research on damage mechanism of bearing current in high power motor

In the running process of high power motor, the shaft voltage and bearing current are sometimes present. Under the combined action of the current and the mechanical load, the corrugated groove is formed on the bearing race. The paper analyzed the causes, forms and characteristics of the early current damage of bearing, studied the relationship between the number of shaft current size and bearing pitting attack damage, presented the theoretical calculation method of the corrugated groove, got the change rule of the corrugated groove spacing with the change of the motor speed and the mechanical load. The experimental results are in agreement with the theoretical analysis, the measurement value of corrugated groove average spacing is very close to its theoretical value, and the average deviation is less than 10 %.

Fluid-enhanced tunable diffraction with an elastomeric grating

We replicate a diffraction grating by soft lithography. Tunable diffraction is accomplished by modifying groove spacing through the application of strain on the elastomeric replica. The range of strain-variable diffraction angles is extended by adding a refracting liquid layer to the grating. Using a water layer, the diffraction angle is tuned from 38 to 33.4 deg with an applied strain of 17.7%. With an equal amount of strain, employing a glycerol layer results in the diffraction angle varying from 38.8 to 34.4 deg. Our experimental results are accurately described by the combined effects of diffraction by a deformable grating and refraction by a fluid with a curved surface.

HEAT TRANSFER ENHANCEMENT AND PRESSURE DROP OF GROOVED ANNULUS OF DOUBLE PIPE HEAT EXCHANGER

This investigation was performed to experimentally investigate the enhancement of heat transfer and the friction of an annulus in a double pipe heat exchanger system with rectangular grooves in the turbulent flow regime. The shell is made of acrylic and its diameter is 28 mm. The tube is made of aluminium and its diameter is 20 mm. Grooves were incised in the annulus room with a circumferential pattern, with a groove space of 2 mm, a distance between the grooves of 8mm and a groove height of 0.3 mm. The experiments consist of temperature and pressure measurement and a flow visualization. Throughout the investigation, the cold fluid flowed in the annulus room. The Reynold number of cold fluid varied from about 31981 to 43601 in a counter flow condition. The volume flow rate of hot fluid remains constant with Reynold number about 30904. Result showed the effect of grooves, which are applied in the annulus room. The grooves induce the pressure drop, the pressure drop in the grooved annulus was greater by about 15.88% to 16.72% than the one in the smooth annulus. The total heat transfer enhancement is of 1.09–1.11. Moreover, the use of grooves in the annulus of the heat exchanger not only increase the heat transfer process, but also increase the pressure drop, which is related to the friction factor.

Thermo-mechanical characterization of laser textured LaMgAl11O19/YSZ functionally graded thermal barrier coating

The ablation resistance and adhesion strength of laser textured and as-sprayed functionally graded LaMgAl11O19/YSZ based thermal barrier coating (FG-TBC) was studied and compared with a duplex coating of LaMgAl11O19 and YSZ (DC-TBC). The thermal barrier coatings were sprayed over Hastelloy C263 using atmospheric plasma spray process (APS). The laser texturing was performed using a picosecond pulsed laser. The width-to-depth ratio and groove spacing were varied to analyse and correlate the significance of groove parameters in providing strain tolerance under extreme thermal loading conditions. The ablation behaviour of the coatings was investigated using a scramjet test rig. The shear force induced through the ablation load spalled the as-sprayed DC-TBC. The thermal stress mismatch instigated through the difference in coefficient of thermal expansion (CTE) between discrete YSZ and LaMgAl11O19 layers led to the failure of the as-sprayed DC-TBC. The as-sprayed FG-TBC exhibited an improved ablation resistance. The varying thermo-mechanical properties along the ceramic layer thickness in as-sprayed FG-TBC minimise the concentration of thermal stress across the coating and imparts better thermal stability. The improved mechanical interlocking of molten splats during re-solidification of five discrete layers of ceramic composites inhibits the concentration of stress around the weak links. Compared to the textured DC-TBCs, the textured FG-TBCs exhibited minimal level of distortion and better resistance to ablation. The textured surfaces restrict the propagation of crack across the top surface and also provide improved strain tolerance. The graded structure minimises the stress built up and improves the coating resistance compared to textured DC-TBCs. The adhesion strength of all test surfaces was analysed following the standard test procedure. The textured surfaces having higher surface roughness (in terms of surface area) exhibited improved adhesion strength. The groove parameters were observed to have significant influence in improving the ablation resistance and adhesion strength of the coatings.

Three-dimensional measurement of turbulent flow over a riblet surface

Measurement of three-dimensional (3D) turbulence over riblet surfaces is challenging due to the small size of the grooves and the requirement for measurement in the inner layer. The capability of two-dimensional (2D) and 3D particle image velocimetry (PIV) and particle tracking velocimetry (PTV) for characterization of the 3D structure of turbulent flow over a riblet surface with groove spacing of 750μm at Reτ=147 (based on friction velocity and half channel height) is investigated. The 2D measurements were carried out using standard planar PIV and high-magnification long-range microscopic PTV (micro-PTV). The investigated 3D techniques include tomographic PIV (tomo-PIV) and 3D-PTV. The results are evaluated in comparison with measurement over a smooth surface and also with direct numerical simulation (DNS) of channel flow by Tsukahara et al. (2005) at Reτ=150. The reflection of the laser light from the smooth and riblet surfaces is significantly different in spite of the wall-parallel illumination. This resulted in biased near-wall (y/H<0.05) measurement using planar PIV. The shortcoming was fulfilled by micro-PTV which could measure the mean velocity profile within the linear viscous sublayer (2<y+<5) and showed a 6.1% reduction of the skin-friction over the riblet surface. Micro-PTV also accurately measured the location of the 〈u2〉 peak and its magnitude reduction over the riblet surface compared with planar PIV. The Planar PIV measured 〈v2〉 peak which is further away from the wall at y/H=0.15 and also the 〈uv〉 profile in the outer layer. The 〈uv〉 profile showed 7.4% reduction of wall shear stress over the riblet surface. 3D-PTV showed a 9.4% reduction of the 〈w2〉 peak and attenuation of v and w fluctuations over the riblet surface compared to the smooth surface through quadrant analysis. The three components of fluctuating vorticity measured by tomo-PIV showed negligible variation over the two surfaces due to the random noise and lack of spatial resolution. Quadrant analysis using planar PIV showed attenuation of the sweep and ejection events near the riblets, which indicates weaker streamwise vortices. Two-point correlation of PIV measurement also demonstrated increase of the coherence of the low and high-speed steaks over the riblets.

Friction properties of groove texture on Cr12MoV surface

To analyze the influence of surface texture on friction properties of Cr12MoV’, ordinary grinder and spinning technology were adopted to obtain the grooved surface morphology of samples, and then the impact of spindle speed and feed in z-direction on surface morphology in the process of spinning was studied. In addition, the corresponding friction coefficient of sample was obtained through friction and wear tests. The results show that the peak clipping and the valley filling were conducted on the grinding surface, which could improve the surface roughness effectively and make the grinding trench-type wear scar more uniform. Both the area ratio of groove and groove spacing increased initially and then decreased with the increase of the spindle speed or the feed in z-direction. As a kind of micro-process, the groove could influence the friction coefficient of sample surface, whose distribution was beneficial to the reduction of friction coefficient. Compared with the surface obtained through ordinary grinding, grooved surface morphology through spinning technology was more conductive to reduce the friction coefficient, which could be reduced by 25%. When the friction coefficient of sample was reduced to the minimum, the texture of groove corresponded had an optimal area ratio and an optimal groove spacing, 37.5% and 27.5 μm, respectively.